SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5e1245ef6b1afc29800e0892e1517acb5885784f9b5d9642034794c5e43adcd' 
  AND token = 'eS4gLmjCuPeMOjFAZZBmJJ6pJuQyLkcY+QA6rZM5OGQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00047

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}